1. Field of the Invention
The present invention relates to an optical waveguide plate for a surface light emitting apparatus and a surface light emitting apparatus using the optical waveguide plate for a backlight of a liquid crystal display, a panel meter, an indicator light, a surface emitting optical switch, and the like.
2. Description of the Related Art
A surface light emitting apparatus has recently been used as the light source for a backlight of a liquid crystal display and the like. The apparatus outputs light emitted from a point source such as an LED element by spreading the light over a plane. In such a surface light emitting apparatus, light emitted by a light emitting diode enters through an incident end face of an optical waveguide plate and exits through the entire area of the light emitting surface thereof. Uniform emission from its light emitting surface is crucial in such a light emitting apparatus. A variety of structures have been proposed for achieving uniformity in emission. For example, Japanese Unexamined Patent Publication No. 2002-42534 discloses such an apparatus.
A surface light emitting apparatus disclosed in Japanese Unexamined Patent Publication No. 2002-42534 has a light guide. This reference describes that in a light emitting apparatus that emits light from a first main surface of a light guide, the light guide comprises a plurality of notches having different shapes from each other on an end face opposite the emission surface of the light source. Each of the notches includes a first face and a second face. The angle made by the first face and an end face decreases as the distance from a center of the end face increases. Also, the angle made by the second face and an end face increases as the distance from the center of the end face increases.